Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$238.75	11.789%	$266.8962	$266.90	$266.90	$266.90
Purchase #2	$142.83	4.833%	$149.733	$149.73	$149.75	$149.70
Purchase #3	$40.61	4.242%	$42.3327	$42.33	$42.35	$42.30
Purchase #4	$88.83	11.547%	$99.0872	$99.09	$99.10	$99.10
Purchase #5	$51.45	5.423%	$54.2401	$54.24	$54.25	$54.20
Purchase #6	$218.56	10.532%	$241.5787	$241.58	$241.60	$241.60
Purchase #7	$214.54	4.218%	$223.5893	$223.59	$223.60	$223.60
7 purchase totals =	$995.57		$1,077.4572	$1,077.46	$1,077.55	$1,077.40